Research Article: A comparison of growth performance and digestive enzyme responses in common carp (Cyprinus carpio) across different culture phases

This study evaluated the effects of biofloc technology (BFT) on growth performance and digestive enzyme activity in common carp (Cyprinus carpio) across two consecutive culture phases: a ۹۰-day nursery phase (۲۵۰-L tanks) followed by a ۱۲۰-day grow-out phase (۱۰۰ m³ ponds). Three treatments were compared: a semi-closed recirculating system (control), a biofloc-recirculating system with indigenous Bacillus spp. (BFT+P), and a biofloc system without probiotics (BFT). Key growth parameters (i.e. specific growth rate, relative growth rate, feed conversion ratio (FCR), protein efficiency ratio, and daily weight gain) and intestinal digestive enzymes (i.e. trypsin, chymotrypsin, amylase, lipase, total protease, and alkaline phosphatase) were monitored. Results showed that BFT+P significantly improved growth and feed utilization. By day ۹۰, FCR was lowest in BFT+P (۱.۱۰±۰.۱۰) versus control (۱.۳۶±۰.۲۰). Digestive enzyme activities were significantly higher in biofloc treatments (p<۰.۰۵), with total protease peaking at ۲۱۵.۵۳±۴.۳۱ U mg⁻¹ in BFT+P at day ۹۰. During the grow-out phase, BFT+P yielded the highest final average weight (۱.۴ kg), the highest harvested biomass (۱۲۲۸±۱۲۳ kg), and the lowest FCR (۱.۲۷±۰.۲۴). Survival rate remained ۱۰۰% across all treatments. Enzyme activities increased time-dependently under biofloc conditions, with the most stable and elevated responses in BFT+P. In conclusion, biofloc system, particularly when combined with indigenous probiotic supplementation, enhances digestive physiology and growth performance of common carp throughout sequential culture phases. These findings offer practical strategies for improving intensive carp aquaculture efficiency.

کلیدواژه ها:

Biofloc technology ، Common carp ، Growth ، Feed conversion ratio ، Digestive enzymes ، Recirculating aquaculture system ، Culture phase